The present invention relates to a shoe interposed between a swash plate and a piston in a swash plate type compressor and more particularly to a shoe made of aluminum alloy and a swash plate type compressor with the shoe.
A swash plate type compressor compresses gas by converting rotation of a swash plate to reciprocation of a piston. A pair of shoes as sliding members is interposed between the swash plate, which rotates at high speed, and the piston, which reciprocates at high speed, to ensure smooth operations of the swash plate and the piston. For example, a swash plate type compressor used for an air conditioner of a vehicle is especially required to be light in weight, and making a shoe, which is one of the components of the compressor, out of aluminum alloy has been conceived to lighten the compressor.
The shoe slides with respect to the swash plate and the piston, and the swash plate and the piston are also often made of aluminum alloy. In such a state, since members made of materials of the same kind slide with respect to each other, seizure easily arises. Therefore, it has been proposed that a layer, which is made of a material other than aluminum, coats at least one of sliding surfaces. Also, when the swash plate or the piston is not made of aluminum alloy, and, for example, when the swash plate is made of iron series, the shoe slides under hard conditions. Thereby, seizure may arise. The shoe is also required to improve its durability because of the hard conditions. In such a state, to inhibit seizure and improve durability, it has been proposed that metal plating, which is made of a material other than aluminum alloy, coats the surface of the shoe made of aluminum alloy.
An unwanted effect is that aluminum alloy is inferior in strength and hardness, so that the aluminum alloy is easily flawed. For example, in a process of assembling a swash plate type compressor, when a shoe abuts against another component upon assembling the shoe, the shoe is easily flawed. When the thickness of the metal plating is relatively thin, a base member made of aluminum alloy is not inhibited from deforming even if hard metal plating coats the is shoe. Therefore, the base member is flawed. Also, for example, a foreign substance such as metallic dust is trapped in between the swash plate and the shoe upon operating, and the shoe is flawed due to the foreign substance. In such a state, when the thickness of the metal plating is relatively thin, the base member is also flawed and deformed. The shoe flawed like that causes the facing sliding surfaces of the swash plate and the piston to be flawed. Particularly, the surface of the swash plate is generally coated with a lubricant layer to reduce friction generated between the swash plate and the shoe due to a hard sliding operation. Therefore, the lubricant layer is torn off by the flaws. As the lubricant layer is removed, the base member or the metal plating of the swash plate progressively abrades, with a consequence of arising seizure. Therefore, the flaws described above should be inhibited as much as possible such that the shoe slides smoothly.
The present invention addresses the above-mentioned problems by improving a layer formed on a shoe.
According to the present invention, a shoe for use in a swash plate type compressor, interposed between a swash plate and a piston, has a base member and metal plating layer. The base member is made of aluminum alloy. The metal plating layer coats at least a part of surface of the base member. The thickness of the metal plating layer ranges from 20 xcexcm to 150 xcexcm.
The present invention also provides a swash plate type compressor having a housing, a drive shaft, a swash plate, a piston, and a pair of shoes. The drive shaft is rotatably supported by the housing. The swash plate is operatively connected to the drive shaft. The piston is accommodated in the housing, and is operatively connected to the swash plate. The pair of shoes is interposed between the swash plate and the piston. Each of the shoes includes a base member and metal plating layer. The base member is made of aluminum alloy. The metal plating layer coats at least a part of surface of the base member. The thickness of the metal plating layer ranges from 20 xcexcm to 150 xcexcm.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.